1. Field of the Invention
This invention is in the field of bicycle axle fasteners, especially cam-operated quick-release types.
2. Description of Prior Art
Conventional quick-release bicycle axle fasteners have a control rod passing through the center of a hollow axle. On one end of the control rod is a lever-operated cam with a follower which presses inward against the axle mounting plate, or drop-out. The opposite end of the control rod is threaded, and has an adjustment nut, which is pulled inward against the opposite drop-out by tension on the control rod. The dropouts are thus clamped firmly between the cam follower and bearing nut on one side, and between the adjustment nut and the other bearing nut on the other side. The dropouts have safety tabs which prevent accidental release of the axle when the cam is open. To release the axle, first the cam must be opened, then the adjustment nut must be manually loosened to clear the safety tabs. This is inconvenient, and results in total loss of the control-rod tension setting, which is controlled by the adjustment nut. The user must re-establish the tension adjustment by trial and error each time the axle is remounted, defeating the idea of a quick-release. Many users are not competent to set this critical adjustment. A poorly adjusted control rod may be too tight, and break, or too loose, and allow the wheel to wobble or detach from the drop-outs.
U.S. Pat. No. 4,805,941 (Segawa, FIGS. 4,5) discloses a quick-release bicycle axle fastener with a safety interlock. His clamping mechanism needs enough range to fully relax the spring (6) of the interlock, since no radial lip is provided for its disengagement from the drop-out with the fingers. Thus, his interlock is inactive when it is needed most, in the released position of the cam lever. When partially rotated, his cam lever is releasable by impact or vibration, defeating the safety. The safety interlock in the present invention works even in the fully released position of the cam lever.
U.S. Pat. No. 5,121,973 (Phillips) discloses a push-button quick-release bicycle axle fastener. It retains the axle by urging a slide under spring force into a special coupling surface on the outer surface of the drop-out. It does not use a cam, or require readjustment for each operation, but it requires a custom drop-out. The present invention uses standard safety drop-outs, and uses a lever-operated cam to clamp the axle firmly to the drop-outs.
U.S. Pat. No. 5,567,020 (Phillips and Stewart) discloses in FIG. 15 a quick-release bicycle axle fastener with a control rod (18) passing through a hollow axle (49). One end of the rod has a cam (1M) which operates a cam follower (15), and the other end has an opposing adjustment nut (11). The cam follower is urged by a spring (13) toward the safety drop-out (43), to provide backup retention of the axle if the cam is open. The follower has a finger grip (16) for release from the safety retention tab (47) of the drop-out. The cam provides enough displacement to clear both safety drop-outs. Disadvantages of this design are as follows: It makes a conforming cam follower impractical, since the follower must leave the cam to perform the interlock function, thus losing its orientation with the cam. To avoid closing the cam on a disoriented follower, a flat cam follower should be used. However, a flat cam follower does not distribute the cam force, and therefore cannot be made of plastic for the smoothest operation. It also allows the cam and control rod to turn relatively easily in the closed position, thus changing the adjustment. Conical centering springs are not practical with this design, since one of them would resist the safety spring (13). These disadvantages are overcome in the present invention.